The zero wave number magnon: Ferromagnetic resonance

Abstract

This initial chapter is devoted to a basic phenomenon in magnetism, the ferromagnetic resonance (FMR). When driven by a microwave field with frequency of the FMR, the magnetization precesses about its equilibrium direction without variation in space. This corresponds to a spin wave with infinite wavelength, or zero wave number. Since the quanta of spin waves are called magnons, the FMR mode corresponds to a zero wave number magnon. Initially, we introduce the main features of magnetic materials necessary to the remainder of the book. Details about the origins of magnetism in matter and the spin interactions can be found in several books listed at the end of the chapter. Then we treat the magnetic resonance phenomenon and go on to study in detail the ferromagnetic resonance in bulk samples and in thin films.